A paramount issue with respect to air travel is that of aircraft cabin security. Of particular importance is isolation of the commercial aircraft passenger cabin from the forward cabin or cockpit. This is necessary in order to thwart unauthorized entry to the cockpit. Current and pending regulations require safety measures to restrict access to the cockpit such as providing a sturdy cockpit door that can be locked from the cockpit side. Yet of course it is necessary for the cockpit crew from time to time to have access to the passenger cabin. For this reason it is desirable to have an alarm system to immediately notify the cockpit crew of any threatening activity occurring in the passenger cabin. The cockpit crew can then take security measures as may be immediately necessary.
The first line of defense to a cockpit intrusion or other cabin disturbance is the cabin attendant. The cabin attendants deal with the minor disturbances but are required to alert the cockpit crew to the more major problems. Hard wired telephone style intercom sets installed in the aircraft are connected between the cabin and the cockpit for communication. At times the need for communication with the crew is urgent such that there is little time to go to an intercom station to call the cockpit. Also, use of the intercom does not per se alert the cockpit crew to the urgency of the incoming message nor afford discretion as may be indicated necessary by the threatening activity.